Summary

Scientists have long known that the human body is a mosaic: All of our cells don't contain exactly the same genome. Every time a cell divides, genetic errors can occur, leading to variations in the DNA sequence that may proliferate and—in some cases—cause disease. Now that genetic sequencing and other technologies have made it easier to recognize mutations that occur in only a subset of cells, researchers are finding more and more harmful mutations hidden among unaffected cells. These findings suggest that in some cases, standard genetic tests in the clinic may be overlooking the underlying cause of genetic disease and underestimating a person's risk of passing such mutations on to their children.